try new mailboxcheck

zimbraAddressAvailable.php

@@ -7,9 +7,10 @@ if(substr($host, 0 - strlen($allowed_host)) != $allowed_host) {
 
 use WHMCS\Database\Capsule;
 define("CLIENTAREA", true);
-require_once(__DIR__ . '/../../../init.php');
+require_once(__DIR__ . '/../../init.php');
 require_once(ROOTDIR . '/includes/dbfunctions.php');
 require_once dirname(__FILE__) . '/zimbraSingle.inc';
+use WHMCS\Database\Capsule;
 
 $whmcs = App::self();
 $productID = $_GET['pid'];